Like we talked about in the chapters on “Macroscopic Properties” and “Biochemistry,” hydrophobic materials do not dissolve well in water. So it makes sense to make waterproof mascaras from something hydrophobic. Waterproof mascaras contain a combination of waxes to make them resistant to washing off in water.
Mood rings were all the rage in the 1970s. They work the same way crystal thermometers work do: thermotropic liquid crystals within a hollow quartz shell respond to temperature changes by twisting, which causes them to reflect different wavelengths of light depending on temperature.